Tube having a length of more than 10 m suitable for high-pressure applications with internal pressure of 2 bar or more, and which is not afflicted with disadvantages exhibited by tubes produced by conventional drawing or cold pilger milling methods. The tube has a wall thickness equal to or larger than the internal diameter, an axial length of 12 m or more, a tensile strength Rm of 850 N/mm.sup.2 or more, and a mean roughness index Ra of the inner wall surface of 0.8 ?m or less. Furthermore, a method of manufacturing such a tube forms a hollow into a tubular intermediate in a first forming step according to the cold forming method, the tubular intermediate thus obtained is annealed, and the annealed tubular intermediate is formed into a tube in a second forming step according to the cold forming method.

Tube having a length of more than 10 m suitable for high-pressure applications with internal pressure of 2 bar or more, and which is not afflicted with disadvantages exhibited by tubes produced by conventional drawing or cold pilger milling methods. The tube has a wall thickness equal to or larger than the internal diameter, an axial length of 12 m or more, a tensile strength Rm of 850 N/mm.sup.2 or more, and a mean roughness index Ra of the inner wall surface of 0.8 ?m or less. Furthermore, a method of manufacturing such a tube forms a hollow into a tubular intermediate in a first forming step according to the cold forming method, the tubular intermediate thus obtained is annealed, and the annealed tubular intermediate is formed into a tube in a second forming step according to the cold forming method.

Composite tube assemblies and thin-walled tubing are disclosed. In embodiments, the composite tube assemblies include a functional tube and a sacrificial tube disposed within or around the functional tube. The sacrificial tube may be removed by exposure to a corrosive media, without substantially affecting the functional tube. Methods of forming composite tube assemblies and thin-walled tubing are also described.

A heat transfer tube is made of aluminum and includes a streak-shaped Zn diffusion layer (6, 106) which is spirally formed on a circular outer peripheral surface in a length direction. According to this heat transfer tube, even in a case where rainwater or dew concentration water is intensively accumulated in a portion of the outer peripheral surface in a circumferential direction, it is possible to obtain a sufficient corrosion resistance.

A heat transfer tube is made of aluminum and includes a streak-shaped Zn diffusion layer (6, 106) which is spirally formed on a circular outer peripheral surface in a length direction. According to this heat transfer tube, even in a case where rainwater or dew concentration water is intensively accumulated in a portion of the outer peripheral surface in a circumferential direction, it is possible to obtain a sufficient corrosion resistance.

One aspect relates to a production method for a ring electrode, to a ring electrode, and to an electrode system. One method for the ring electrode includes providing an outer element, including an outer tube, providing a first inner element, including a first inner tube having a first core of a sacrificial material, providing a second inner element, including a second core of a sacrificial material, forming a composite tube by arranging the first inner element and the second inner element inside the outer element, the first inner element and the second inner element being arranged off-center with respect to one another, drawing the composite tube in a longitudinal direction of the composite tube, separating a composite tube disk from the composite tube, removing the sacrificial material of the first core, and removing the sacrificial material of the second core in order to obtain a contacting opening in the ring electrode.

One aspect relates to a production method for a ring electrode, to a ring electrode, and to an electrode system. One method for the ring electrode includes providing an outer element, including an outer tube, providing a first inner element, including a first inner tube having a first core of a sacrificial material, providing a second inner element, including a second core of a sacrificial material, forming a composite tube by arranging the first inner element and the second inner element inside the outer element, the first inner element and the second inner element being arranged off-center with respect to one another, drawing the composite tube in a longitudinal direction of the composite tube, separating a composite tube disk from the composite tube, removing the sacrificial material of the first core, and removing the sacrificial material of the second core in order to obtain a contacting opening in the ring electrode.

Engine and its camshaft, camshaft manufacturing method, the camshaft comprises a central shaft having an axial hole, the central shaft has a fitting section, the outer circumference of a cross section at any axial position of the fitting section is a polygon; a first cam and a second cam, the first cam and second cam are respectively installed on the fitting section of the central shaft and are spaced axially. Such a structure has the advantages of higher torque transmission, simpler structure, simplified manufacturing process, shorter manufacturing time consumption and reduced cost.

Engine and its camshaft, camshaft manufacturing method, the camshaft comprises a central shaft having an axial hole, the central shaft has a fitting section, the outer circumference of a cross section at any axial position of the fitting section is a polygon; a first cam and a second cam, the first cam and second cam are respectively installed on the fitting section of the central shaft and are spaced axially. Such a structure has the advantages of higher torque transmission, simpler structure, simplified manufacturing process, shorter manufacturing time consumption and reduced cost.

A method produces an inner spiral grooved tube using a first drawing die, a second drawing die, and a revolving flyer. The method includes two twisting-drawing steps. The first twisting-drawing step forms an intermediate twisted tube by reducing the diameter of a linear grooved tube, which has plural straight grooves formed along the longitudinal direction on its inner surface, by passing the linear grooved tube through the first drawing die and then by revolving the liner grooved tube wrapped around the revolving flyer with the revolving flyer, in conjunction with imparting twist to the linear grooved tube. The second twisting-drawing step forms the inner spiral grooved tube by reducing the diameter of the intermediate twisted tube by passing the intermediate twisted tube, which revolves with the revolving flyer, through the second drawing die in conjunction with imparting twist to the intermediate twisted tube.